At present, there is a great interest in catalytically converting biomass-derived molecules to hydrocarbons and chemicals [1-3]. Biomass-derived reactants are typically highly functionalized, water-soluble molecules; therefore they are more suitably processed in the aqueous phase. However, conventional catalysts and supports suitable for gas phase reactions may not be suitable for aqueous phase reactions at temperatures in excess of 200° C. because the oxide supports can react with water and lose surface area. For example, the surface area of SBA-15 silica decreased from 930 to 31 m2/g after a hydrothermal treatment (liquid water at 200° C. for 12 h) [4]. In an aqueous phase reactor, γ-alumina was converted into a hydrated boehmite phase with significantly decreased acidity and surface area, which caused the sintering of the supported Pt metal particles [5] and the encapsulation of catalytic Pt sites by the hydroxylated alumina layers [6]. Further, it has been reported that the zeolite structure changed when exposed to aqueous phase conditions [7]. Consequently, a central challenge for production of biorenewable fuels and chemicals is the development of catalytic materials that are hydrothermally stable during aqueous-phase reactions.
Solid acid catalysts have served as important functional materials for the petroleum refinery industry and the production of chemicals [8, 9]. Niobium oxide is an important solid acid catalyst that can be used extensively in important biomass reactions, such as dehydration, aldol condensation, hydrolysis and ketonization [10, 11]. Mesoporous niobium oxides with high surface areas recently have been synthesized by template-assisted self-assembly and antisolvent precipitation routes [12-15]. However, pure niobia was found to crystallize and deactivate quickly in liquid water when the temperature was higher than 200° C. [16]. To address this problem of hydrothermal stability, one approach that has been demonstrated to be effective is to disperse a thin film of niobia on a mesoporous support by atomic layer deposition (ALD). However, ALD requires sequential reactions with two separate reactants and multiple cycles to achieve niobia coatings.[4] Therefore, a simple one pot synthesis to achieve hydrothermally stable niobia would be desirable.